Q: API Requests that need Authorization return CORS error Initial Problem
I work on a web application (react) that accesses data via an API. The API runs for development reasons on a docker container on my local machine. Simple GET requests (via axios) got me CORS complications (...has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.).
A bit of researching solved my problem by running a nginx reverse proxy in another container. I basically used this configuration for the nginx server.
New Problem
As I progress in building my application, I come to a point where I need to send the JWT to the API to access and alter some entries. Requests that need sending a JWT again get me CORS error messages.
The API checks the JWT signature (RS256 generated). I just have to forward it to the API server.
ALSO: simple curl requests with the JWT from the console are working.
Configuration

*

*axios


const axiosConfig = {
    responseType: "json",
    withCredentials: false,
    mode: "no-cors",
    headers: {
        'Access-Control-Allow-Origin': "*",
        'Access-Control-Allow-Credentials': true,
        'Access-Control-Allow-Methods': 'GET,PUT,POST,DELETE,PATCH,OPTIONS',
        'Content-Type': 'application/json',
        'Authorization': 'Bearer <JWT as string>',
    },
};

const apiGetRequest = async (route, callback) => {
    try {
        const apiUrl = URL + route;
        axios.get(apiUrl, {
            axiosConfig
        })
            .then(res => {
                callback(res);
            })
            .catch(function (error) {
                console.log(error);
            });

    } catch (error) {
        console.log(error);
    }
}


*

*nginx configuration


*Docker Image for api
version: "3.9"

services:

    db:
        image: mariadb:latest
        container_name: db
        env_file:
            - ./mariadb/.env
        volumes:
            - ./mariadb/create-schema-docker.sh /docker-entrypoint-initdb.d
            - db-data:/var/lib/mysql
        ports:
            - 3306:3306

    rest:
        image: mds4ul/station-registry:latest
        container_name: api
        environment:
            - DB_HOST=db
            - CONTEXT_PATH=api
        env_file:
            - ./rest/.env
        depends_on:
            - db
        ports:
            - 80:8080

volumes:
    db-data:


Questions

*

*Why do I get CORS errors for requests where a jwt is needed and not for requests that do not require one?

*Which part do I have to change to make this work?


A: So answer another question to an embarrassing easy problem of mine.
I switched to an express.js proxy server with the following configuration:
const express = require('express')
const app = express()
const axios = require('axios')
const cors = require('cors')
var bodyParser = require('body-parser')

app.use(cors({
    origin: '*'
}))
app.use(bodyParser.json())

require('dotenv').config()

const headers = {
    "X-Authorization": <token>,
}

app.get(':endpoint([\\/\\w\\.-]*)', function (req, res) {
    const endpoint = (process.env.API_BASE_URL).replace(/\/$/, "") + req.params.endpoint;
    axios.get(endpoint, { headers }).then(response => {
        res.json(response.data)
    }).catch(error => {
        res.json(error)
    })
})
app.listen(3001)

I assume I just could not figure out my nginx configuration for this use case. So with express.js I can access now resources which need authorization.
